Fluid spring perforating unit



Aug- 28, 1955 P. H. TAYLOR 2,760,575

FLUID SPRING PERFORATING UNIT Filed Sept. 19, 1950 f;

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INVENToR. Paal H. Taz/lor A iorrvegg. l

FLUID SPRING PERFRATING UNIT Paul H. Taylor, North Tonawanda, N. Y., assignor to Wales-Strippit Corporation, North Tonawanda, N. Y., a corporation of New York Application September 19, `1950, Serial No. 185,606-y 20 Ciaims. (Cl. 164-94) This invention relates to a Work-performing instrumentality of the type characterized by a resilient means in which energy is stored during working strokes of the instrumentality so that suchenergy may be releasedl upon completion of the working strokes to restore, or aid in restoring, the instrumentality, or parts thereof, to their original positions; and more particularly the invention is concerned with such a resilient means wherein energy is stored by compressing a fluid medium and released by permitting the compressed tluid medium to expand.

The resilient means of the invention is characterized by features which enable it to be readily adaptedto various kinds of instmmentalities, although particularly` desirable results may be obtained by incorporating the resilient means in instrumentalities in which the space available is limited and in instrumentalities in which the forces to be stored and released are substantial. The resilient means of the invention may, therefore, be employedxto partielle` lar advantage in punchingand perforating apparatus `of the kind wherein the punch and die elements are-:associ` ated in a self-contained assembly so that the movable element may be actuated by the ram of a standardpress, the resilient means in such case being operative to return the punch to its original position during the return stroke of the ram and in so doing strip the work from thepunch.

Heretofore, it has been the practice to employmechanical springs for developing the forces required in stripping the work from a punch after a working stroke of the latter. The use of mechanical springs for this pur'- pose has imposed highly objectionable limitationswith respect tothe thickness and character of the material which may be punched, or perforated, as the availability of the apparatus for any particular application'ispofne` cessity, dependent upon the capacity of the stripping apparatus to withdraw the punch after the punching, or perforating, strokes. Because of this limitation, it hasbeen impractical heretofore, for example, to perforatemetal stock substantially over Mi thick. It has also been-impractical to exceed a hole diameter much larger'thaniZ without involving the use of costly stripping apparatus. This has been particularly true in the case of large punches as Va large spring surrounding such a punch is unsatisfactory for stripping because in the larger diameters a given wire size of spring provides a soft spring which has insu'icient stripping capacity unless pre-loaded to'a substantial degree. Pre-loading of itself is objectionable as it imposes severe stresses on the punch and stripping apparatus.

The use of mechanical springs forr stripping purposes has other objections,V a seriousone being that such springs require considerable space and hence increase the height of the punch column. They also add to the width of the assemblies and thereby prevent the forming of'holes as close together as would otherwise be possible. Mechanical springs'have thefurther objection that they are subject to fatigue and frequently to breakage, particularly if the ram of the press by which the moving element of States Patent ice the punching, or perforating, assembly is to be actuated, isV permitted'toovcrtravel. to an extent such as tofcause bortoming upon :on another of the various convolutions of the springs'.

The invention contemplates, as in the case of my copending application lSerial No. 185,604, tiled September if), 1950, now patent No. 2,732,898, the use of a fluid medium, preferably an oil or other suitable liquid, which is compressed and reduced in volume during the working stroke lof` the work-performing instrumentality, whereby toy store energy in said medium which maybe releasedby permittingtheflatter to expand and in so doing returnthe work-performing instrumentality' to its normal position upon completion of the working stroke. The use of oil as the compressible fluid has the advantage that it 4may be subjected, for example, to a pressure of 50,000 p.- s. i., the volume of the oil thereby being reduced approxi-l mately l3%, although the volume of silicone, and other oils may be'reduced as much as 26% bythe same pres sure. As the maximum possible compressibility of a rnechanicallspring will not ordinarly exceed 1,000 p. s.- i., it will beireadily appreciated that the resilient means of the invention is available to provide stripping forces; within the same space,y far exceedingv such forces. as can be ob tained with the use of a mechanical spring,v Although; for various reasons, .the gain ratio-may not be as high-ras 50 to 1,.an overall gainof some'S or 1,0y ,to-1 can betreediiy attained. In other words, it is possibley byusing': a fluidf medium in the manner-contemplated to readily-dci# velop stripping forces 800% vto 1,000% greater-than can be developed by a mechanical springrwithin the. same space limitations.

The principal object of the` invention is to provide a resilient means ofthe character generally described Which may be availed ofto store energy in such a manner that high work-performing forces'may bc'developed within a minimum ofspace.

Another object is to provide a resilient'means-Which may be associated-with punching andper-foratingv apparatusin such a manner that much thicker stock maybe punched, or perforated, than has heretofore been possible when. thel stripping forces have been providedv by mechanical springs.

A still further object is to provide a resilient means which may be associated with a work-performing instrumentality in such a manner that the force developed will be directly proportional tothe force required torestore the instrumentalityy to its original condition upon completion of a working stroke.

A still further object is to provide a resilient means which.v is linear in action and which requires nopreloading.

A stillfurther object is to provide a resilient means which may be located wholly at one sideof the workperforming member and which, therefore, enables a shorter, stiifer and stronger punch column to be attained and at the same time'reduces `the press gap.

.Arstill further object is a punch, or perforating, device wherein the resilient means is so designedand 1ocated `with respect to the punching element that anarrow device is provided, this having the advantag'ethat the device is particularly adaptableto the punching of closely-spaced holes, orperforations.

A still further object is to provide a punching-orpe'r forating device which isso designed' that the use'ofme'- chanical springs is rendered unnecessary.Y

A still furthervobject is to provide a punching, or perforating, assembly having a novel design and arrangement ofthe parts, whereby to provide for simplicity and'economy in construction and insure dependability inoperation.

The invention is illustrated in the accompanying drawings, wherein:

Figure 1 is a side elevational View, partially in section, of a self-contained perforating assembly embodying the features of the invention;

Figure 2 is a fragmentary, sectional view illustrating the relation of the parts upon completion of a working stroke of the punch and prior to the return of the parts to the positions shown in Figure l;

Figure 3 is a fragmentary top plan view of the portion of the assembly shown in Figure 2; and

Figure 4 is a detail section taken along line 4 4 of Figure 2.

The features of the invention are illustrated in connection with a perforating tool. The latter, as shown, is in the form of a self-contained assembly and includes a C-frame for carrying the punch and die elements 21 and 22, respectively. The punch 21 is guided for axial movement in a guiding and stripping sleeve 23. Relative axial movement, within predetermined limits is permitted between the punch 21 and the sleeve 23 by a ball 24. The latter is accommodated in confronting, axially-extending grooves and 26 formed respectively in the punch and sleeve, it being noted (see Figure l) that upward movement of the punch with respect to the sleeve 23 is arrested as the lower end of the groove 25 approaches the upper end of the groove 26. The ball 24 may be initially introduced into the grooves 25 and 26 through an opening 27 in the sleeve 23. The parts are so designed that in the normal use of the tool the lower end of the groove 25 will not descend far enough to permit escape of the ball 24 into the opening 27. This is illustrated in Figure 2 wherein the punch and guiding and stripping sleeve are shown at the lower limits of their ranges of movement.

In accordance with the invention, the punch 21 is formed with a head 28 which extends laterally in the direction of the closed end of the frame 20 and which overlies a laterally extending projection 29 formed on the guiding and stripping sleeve 23.

A cylinder 30 is located between the head 2S and the projection 29, the said cylinder having spaced-apart, axially aligned pistons 31 and 32. The former engages the under side of the head 28 while the latter engages the upper side of the extension 29, the guiding and stripping sleeve 23 being cut away as indicated at 33 so that the cylinder 30 may be spaced close to the shank of the punch. The cylinder 3i), between the spaced-apart pistons 31 and 32, communicates through a restricted port 36 with a container 34 which is in the form of a cartridge, the container having an open end which is threaded to receive a threaded extension of the cylinder 30. The cylinder 30 and the container 34 provide a reservoir for accommodating a compressible fluid, such as oil or the like, and in the use of the tool the cylinder and container are filled with said uid. Normally the fluid is operative to support the punch and guiding and stripping sleeve in the elevated positions and the pistons 31 and 32 in the spaced-apart relation shown in Figure l.

A guide pin 37 which is carried by the upper arm of the frame 20 has an inner extension which occupies a groove 38 in the lower end of the guiding and stripping sleeve to prevent turning of the latter as it is caused to reciprocate during the use of the tool.

The cylinder 30, the pistons 31 and 32 and the container 34 may, as shown, constitute a sub-assembly, the container being multi-sided in transverse cross-section and being removably secured by clips 30a in a conforming channel 40 in the upper face of the upper arm of the frame 20.

The tool may be operated by a conventional press as illustrated in Figure 2, the ram of the press being indicated at 41 and the bed at 42. The parts of the tool and the press parts are shown in the positions which they occupy upon completion of a Working stroke.

during which the punch 21 has cooperated with the die 22 to perforate a work-piece 43. During the initial part of the working-stroke, the movement of the punch is transmitted by the pistons 31 and 32 and the uid between said pistons to the guiding and stripping sleeve and the latter is caused to approach and engage the Workpiece in advance of the punch. As the working stroke continues and as the guiding and stripping sleeve 23 remains stationary, the punch is driven through the Workpiece, as illustrated, while the fluid in the cylinder 30 and container 34 is compressed. As shown in Figure 2, compression of the fluid medium occurs as the lower piston 32 remains stationary While the piston 31 advances toward it. Energy is thereby stored in the compressible luid, and upon return of the ram 41 the compressed uid is permitted to expand to restore the parts to the positions shown in Figure l and thereby strip the punch from the work-piece, it being noted that as a result of the larger size of the piston 31 with respect to the piston 32 (and the unbalanced piston areas thus provided) the parts all move upwardly.

The use of a compressible fluid in the manner illustrated and described has the advantage that stripping forces far exceeding any which may be obtained by conventional mechanical springs are produced within a small space, thereby enabling the punching of materials of much greater thickness than has heretofore been possible with mechanical springs. The location wholly at one side of the punch of the means in which the stripping forces are stored enables the use of short punch columns of great strength and at the same time provides a narrow construction which adapts the tool particularly to the punching of closely spaced holes.

The ball 24 not only serves as a stop to tix the upper limit of the range of movement of the punch with respect to the sleeve but is employed primarily as an antifriction means for preventing binding of the punch in the sleeve as a result of the rocking moment induced by the resistance to compression `of the fluid in the cylinder 3i) and container 34 during the working strokes of the punch.

The features of the invention have been illustrated, by way of example, in connection with a perforating tool wherein the parts are in the form of a self-contained assembly. It will be understood, however, that the features of the invention are not necessarily limited to such self-contained assemblies and that the head 28 of the punch need not necessarily be employed for actuating the piston 31 to compress the Huid in the cylinder 3l? and the container 34 in the manner and for the purpose contemplated.

I claim as my invention:

l. In a punching apparatus, a punch having a laterallyprojecting head, a sleeve in which the punch is slidable and an end `of which serves as a stripper, said sleeve having a limited range of movement along the same axis as the punch and being provided with a laterallyprojecting shoulder which is aligned with said head radially of the common axis of the punch and sleeve, one of the limits of the range of movement ofthe sleeve being established by said shoulder, and means located wholly at one side of said punch between said head and shoulder in which energy is stored during the working stroke of the punch, when said punch is moving relative to said sleeve, and from which energy is released upon completion of said working stroke to return the punch to its original position and in so doing'strip the work from the punch, and a lost-motion connection between said punch and said sleeve permitting said punch to move relative to said sleeve during the working stroke of said punch and constraining said sleeve to move with said punch during the latter part of the return stroke of said punch to return said sleeve toits original position` 2. In a punching apparatus, a punch, a sleeve in which the punch is slidable and an end of which serves as a stripper, means located wholly at one side of said Bunch andinterpose'd between saidy punch and' saidfsleeveand adapted to be actuated uponfmovem'ent of isaidepunch relative to said sleeve during `the working'stroke of 'the punch to store energy andv from-which energy is released uponl completion of said `working stroker to' return the punch to its original position and in soy doing strip the w'or'kfr'om the punch, antifriction'means `at theoppo'site side of saidl punch for preventing vbindingofsaidV punch insaid sleeve as a result of the rocking moment induced by" said Ifirst mentioned means, said antifriction' means providinga'lost-'motion connection 'between said punch and 'said' sleeve permitting said punch to move relative to' said'sleeve during 'the working strokeoff said punch and constraining said sleeve to move with said punch during the latter part of the return stroke 'of said" punch tov return said sleeve to its original position.

3. In'a'punching apparatus,` a punch having a lateral extension, said punch being reciprocable for its` working andI ireturnstrokes, a reciprocablestripper in which the punch is reciprocable, saidl stripper beingpfori'ned 'with alateral' extension and Vbeing axially movable between predetermined A limits, the last-named extension :being aligned radially'of the axis of saidstripper with the rs'tnamedextension, a liquid reservoir' filled with a corn; pressible liquid, and means located' between said lateral extensionsand connected to said punch and said stripper, respectively, and operatively connected to said liquid to compress said' liquid' during the working stroke of the punch,` whereby' upon completion of said Working strokesaid liquid may be permitted to expand to return the sleeve and punch to their original positions and' in sodoing strip the work' from the punch, and a lostmotionl connection between said Ipunch and said'stripper permitting movement of said punch'relative tosaid strip# per during the working stroke of' said punch'after said stripper has engaged the work, and effecting"V return of said stripper on the latter part of the return stroke of said punch.

4. In a punching apparatus, a punch which is re` ciprocable for its working and return strokes, said punch having" a lateral extension, a reciprocable stripper in which said punch reciprocates, said stripper also having alateral extension which is aligned with 'the first-named extension, a cylinder for a body of liquid, a liquid reservoirwhi'ch communicates with said cylinder and Iwhich is located at one side of the latter, said cylinder and reservoir being filled with a compressible liquid, said cylinder being open at both ends, a pair of spaced-apart axially-aligned pistons reciprocable in the open ends of said cylinder-'to compress said liquid during the working stroke of the punch, whereby upon completion of said working stroke said liquid may be permitted to expand and' thereby return the punch to its original position, `one of said pistons being engaged with one of said extensions andthe other of said pistons being engaged with the other" of said extensions, and a lost-motion connection between said punch and said stripper permitting -said punch to move'relative to said stripper, after said stripper hasengaged the work on the working stroke of said punch, and causing said punch to move said stripper on the' latter part of the return stroke of said punch to return said stripper to original position, the effective area yof the piston which engages the first-named lateral extension being greater than the effective area of the piston which engages the second-named lateral extension.

5. in a punching apparatus, a punch which is reciprocabie for its working and return strokes, said punch having a lateral extension, a reciprocable stripper around saidpunch, said stripper also having a lateral extension which is aligned with the first-named extension, a cylinder for a body of liquid, a liquid reservoir which communicates with said cylinder and which is located at one side of the latter, said cylinder and reservoir being lled with a compressible liquid, said cylinder `having guideopenings at its opposite ends, and a pair of spaced! apart',l axially-aligned reciprocable pistons of diierent areas -re'cir'irocable in 'said two" guide openings of -said cylinder, respectively, for compressing 'said'liqu'id 'dur'- ing'the working strokeof the punch, ,oneof said'pistons being engageable withone of` said extensions arid the other of said pistons beingfengageable -withl the other of said extensions, whereby up'o'nA expansion"of said liquid, on completion ofthe working stroke,'the punch will be returned to its original position', and 'a los't`- motion connection between said 'punch and"said"stripper permitting said punch to move relative to said stripper, after said stripper has engaged the work on the working stroke of said punch,r and 'causing' `said punch to move said stripper :on the latter part of the'return stroke of said punch to return said stripperto original position;

6, In a vpunching apparatus, a rectilinearly reciprocable punch having a lateral extension, 'a sleeve iti which said ypunch is reciprocable and is guided and one end of which serves as a stripper,- saidk sleeve' havinglaflat'- eral extension spaced laxially of the 'sleeve axisl from the first-named lateral` extension but aligned' therewith radiallyof' the sleeve axis, a closed chamber filled with liquid,'and a pair of pistons located between said lateral extensions `andy reciprocablethrough vopenings in opposite ends ofsaid chamber, respectively, forv compressingthe" body of liquid in said chamber duringthe working stroke `of said punch,l whereby said liquid by its expansion may returnsaid punchto original position upon completion of sa'id'working stroke. p

7. In a punching apparatus,`a rectilinearly reciprocable punch having a lateral extension, va re'ciprocable sleeve in`whichsaid punch is reciprocable'l and is guided and one'end of*` which serves as va stripper," said sleeve being positioned so thatsaid yone'end thereof engages the 'work to llimit themovement of saidsleeve in' one direction while the punch continues lits movement in said one' direction t6 performits work, said sleeveha'vingv a lateral extension spaced rectilinearly fromv the first-named ex tension but aligned rectilinearly withthe rs'tenamed ex' tension, a closed chamber filled with a compressible' liquid and located between said extensions, a piston" re-' cipro'cablein an opening in oneend of said Achamber and operatively connected to said punch to reciprocate therewith, and a second pistonaxially aligned With'the first piston'and reciprocable in an opening in the opi posite' end of said chamber and operatively connected to said sleeve,` the effective operating area of the first piston being greater than the enecting operating area'of the second piston, and a lost-motionco'nnection between said sleeve and said punch permitting limited axial movement between them in both directions.

8. ln apparatus of the character described,` a recip rocable punch, a reciprocable .stripper in whichv said punch is slidable, a body of liquid located wholly at one side of said punch, means connecting said-punchto said body of liquid to transmit force from said punch to said body of liquid during the working stroke of said punch, means connecting said stripper to said body of liquid to transmit force applied to said body of liquid to said stripper until said stripper engagesV a'workpiece, the first named means acting thereafter to compress said body of liquid during the remainder of the working stroke of said punch, whereby upon completion of said working stroke said body of liquid may expand to return said punch to its original position, and a lost-motion connection between said punch and said stripper causing' said punch to return said 'stripper'to original position on the latter part ofthe return strokeoffsaid punch.

9. ln apparatus of the character described, a punch which is reciprocable'to effect its working'` and 'return strokes, a reciprocable stripper in which lsaid punch is slidable, a container disposed at -one sideof said punch and filled with a body of-compressibleliquid, al first piston reciprocable insaid container-fand-connected to' said punch to reciprocate therewith, i a second piston spaced from the first piston but also reciprocable-in said stripper, said first piston having a greater effective area than said second piston, and a lost-motion connection between said punch and said stripper permitting said punch to move relative to said stripper, after the stripper has engaged the work on the working stroke of said punch, and causing the punch to move the stripper on the latter part of the return stroke of the punch to return the stripper to original position.

10. In apparatus of the character described, a punch which is reciprocable to etiect its working and return strokes, said punch having a lateral extension, a reciprocable stripper in which said punch is slidable, a container disposed wholly at one side of said punch and filled with a body of compressible liquid, a piston reciprocable in said container and positioned to be engaged by said lateral extension during the working stroke of said punch and to engage said lateral extension to eEect the return stroke of said punch, a second piston spaced from the first-named piston but also reciprocable in said container, said second piston being connected to said stripper to move therewith, and a lost-motion connection between said punch and said stripper permitting said punch to move relative to said stripper, after said stripper has engaged the work on the working stroke of said punch, and causing said punch to move said stripper on the latter part of the return stroke of said punch to return said stripper to original position.

ll. In a punching apparatus, a punch reciprocable for its working and return strokes, a reciprocable stripper in which said punch is reciprocable, a cylinder filled with a compressible liquid, a pair oi spaced, axiallyaligned pistons reciprocable in said cylinder and connected to said punch and said stripper, respectively, and a lost-motion connection between said punch and said stripper permitting said punch to move relative to said stripper, after said stripper has engaged the work on the working stroke of said punch, and causing said punch to move said stripper on the latter part of the return stroke of said punch to return said stripper to original position, the effective area of the piston which is connected to said punch being greater than the effective area of the piston which is connected to said stripper.

12. In a punchingr apparatus, a punch reciprocable for its working and return strokes, said punch having a lateral extension, a reciprocable stripper in which said punch is reciprocable, said stripper also having a lateral extension which is aligned with the first-named lateral extension, a cylinder lled with a compressible liquid, a pair of spaced, axially-aligned pistons reciprocable in said cylinder and abutting, respectively, against the two extensions, and a lost-motion connection between said punch and said stripper permitting said punch to move relative tosaid stripper, after said stripper has engaged the work `on the working stroke of said punch, and causing said punch to move said stripper on the latter part of the return stroke of said punch to return said stripper to original position, the effective area of the piston which abuts the first-named extension being greater than the effective area of the piston which abuts the second-named extension.

13. Perforating apparatus comprising a C-frame having an upper and a lower arm, said upper arm being rigid with said lower arm, a die mounted in said lower arm, a sleeve reciprocable in said upper arm, a punch reciprocable in said sleeve in axial alignment with said die, a container located wholly at one side of said punch and carried on said upper arm, a body of compressibe liquid filling said container, means connecting said punch to said body of liquid so that on a working stroke of said punch force is transmitted to said body of liquid, f.

and means connecting said sleeve to said body of liquid so that said force is transmitted to said sleeve to move said sleeve with said punch until said sleeve engages the work, said punch thereafter moving relative to said sleeve and compressing said body of liquid whereby upon iii) ing stroke to strip said punch from the work and return it to its original position, said stripper being returned completion of said working stroke said liquid expands to strip the punch from the work.

14. In apparatus of the character described, a punch which is reciprocable to eiect its working and return strokes, a reciprocable stripper in whichsaid punch is slidable, a container, a compressible liquid filling said container, a first piston reciprocable in said container and connected to said punch to reciprocate therewith, a second piston spaced from said first piston and also reciprocable in said container, said second piston being connected to said stripper, said punch and stripper moving together on a working stroke until said stripper engages the work, and, said punch thereafter moving relative to said stripper causing said liquid to be compressed in said container between said pistons, said liquid expanding on completion of said working stroke to Strip said punch from the work, and means for returning said stripper to its initial position.

15. In apparatus of the character described, a C-frame having an upper and a lower arm, said upper arm being rigid with said lower arm, a die mounted on said lower arm, a stripper reciprocable rectilinearly in said upper arm, a punch reciprocable rectilinearly in said stripper, said punch having a lateral extension, said stripper having a lateral shoulder spaced from said lateral extension but aligned therewith rectilinearly, a cylinder open at both lends and interposed between said extension and shoulder and carried on said upper arm, a pair of spaced, axially aligned pistons reciprocable, respectively, in the ends of said cylinder, said pistons closing said cylinder, a compressible liquid filling said cylinder and against which said pistons are operable, one of said pistons being connected to said extension and the other of said pistons being connected to said shoulder, said punch and stripper moving together on a working stroke of said punch until said stripper engages the work, said punch and said one piston thereafter moving relative to said stripper and said other piston to compress said liquid in said cylinder between said pistons, said liquid expanding on completion of the working stroke to strip said punch from the work and return it toward starting position.

16. In apparatus of the character described, a C-frame, a die mounted in the lower arm of the C-frame, a stripper reciprocable in the upper arm of the C-frame, a punch reciprocable in the stripper in axial alignment with said die, a cylinder located wholly at one side of said punch and carried on said upper arm, a compressible liquid filling said cylinder, said cylinder being open at opposite ends, a pair of spaced pistons reciprocable in the opposite ends of said cylinder and operable against said liquid, said pistons closing said cylinder, means connecting said punch to one of said pistons, means connecting said stripper to the other of said pistons, the effective area of the piston which is connected to said punch being greater than the effective area of the piston which is connected to said stripper, and an antifriction, lost-motion connection between said punch and stripper at the side of said punch diametrically opposite said cylinder, said punch and stripper moving together on a working stroke of said punch until said stripper engages the work, said punch moving thereafter relative to said stripper to compress said liquid in said cylinder, said liquid expanding on completion of the workto its original position on return of said punch through its lost-motion connection with said punch.

17. A resilient device comprising a first member, a cylinder, a compressible liquid illing said cylinder, a irst piston reciprocable in an opening in one end of said cylinder, said first member being positioned to engage said iirst piston on movement of said first member in one direction, a second piston reciprocable in an opening in the other end of said cylinder, a second member positioned to be engaged by said second piston to be moved thereby until said second member is stopped by means external of said device positioned to be engaged by said second member said second piston having a smaller eiective area than said iirst piston, said first piston being movable inwardly of said cylinder uponL application of an outside force to said first member, and said liquid serving to transmit force from said first piston to said second piston to move said second piston and said second member until said second member has been stopped, said liquid being thereafter compressed upon movement of said first piston toward the second piston on continued application of said outside force to said irst member, said liquid expanding upon release of said outside force to return said rst piston and said rst member to their original positions, and means for returning said second piston and second member to their original positions comprising a lost-motion connection between said first and second members.

18. A resilient device comprising a tubular guide, a member reciprocable in said guide, a cylinder offset from the axis of said guide, a compressible liquid lling said cylinder, a first piston reciprocable in an opening in one end of said cylinder, means connecting said member to said piston, a second piston reciprocable in an opening in the opposite end of said cylinder, means connecting said guide to said second piston, said first piston being movable inwardly of said cylinder upon application of an outside force to said member and said liquid serving to transmit force from said rst piston to said second piston to move said second piston and said guide in one direction until said guide is stopped by means external of said device positioned to be engaged by said guide, said liquid being thereafter compressed upon movement of said iirst piston toward said second piston upon continued application of said outside force to said member, said liquid expanding upon release of said outside force to return said first piston and said member to their original positions, and means for returning said second piston and said guide to their original positions.

19. In an instrumentality of the character described, a holder having means formed to provide a bore, a punch reciprocable axially in said bore, said means and said punch being formed with confronting channels which are closed at their ends and which extend in the direction of movement of said punch, an anti-friction member which has anti-friction engagement with both of said channels to roll therein as the punch moves in said bore, and resilient means located wholly at the diametrically opposite side laterally of the axis of said punch from said channels to be compressed when `said punch is moved in one direction and which is operative, upon expansion to move said punch in the opposite direction, said antirriction means being operative to limit movement of the punch in said bore and to prevent binding of said punch in said bore when said resilient means is acting on said punch for the purpose described.

20. Perforating apparatus comprising a holder, a sleeve reciprocable axially in said holder and having a seat at one side, a punch reciprocable in said sleeve and having a lateral extension which is provided with a seat aligned with the first-named seat, resilient means located wholly at one side laterally of said punch and interposed between said seats and which is compressed when said punch is moved relative to said sleeve on the working stroke of said punch and which is operative, upon eX- pansion, to withdraw said punch from the work, said sleeve and said punch being formed with confronting channels at the opposite side laterally of said punch from said resilient means which extend in the direction of movement of said punch and which are closed at their ends, and a rolling anti-friction element which engages in both of said channels and which is operative to prevent binding of said punch in said sleeve and to limit the movement of said punch in the sleeve when said resilient means is acting to withdraw said punch.

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